1. Technical Field
This invention generally relates to improved steering linkage for riding power trowels, and more particularly to devices for applying a torque force to a steering linkage lever or a tilting gear box.
2. Background
Riding power trowels have been known in the prior art for many years. The principals upon which they rely to provide directional control are also well known and set forth with particular clarity in the Holtz, U.S. Pat. No. 4,046,484, the teachings of which are herein incorporated by reference.
Basically stated, riding power trowels require at least two tiltable gear boxes which are operatively connected to a plurality of troweling paddles arranged in a radial array to form tiltable troweling assemblies. These tiltable troweling assemblies are counter-rotated, and when they are both tilted inwardly or outwardly, depending upon the direction of the counter rotation, the power trowel will move either forward or backward across the concrete surface being troweled. When they are tilted in the opposite direction, the riding power trowel will move in the opposite direction.
Also typical in the prior art at least one of the tiltable power trowel assemblies is tiltable forward and backwards, and depending upon the direction of rotation, if the trowel assembly is tilted forward, it will impart a sideways motion to the trowel in one direction, and if the trowel assembly is tilted backward, it will impart a motion in the opposite direction.
All of this is well known and fully explained in Holtz, U.S. Pat. No. 4,046,484.
In the prior art, the operator typically is seated atop of the power trowel and has available to him two steering handles, to which steering linkage is attached, in various configurations, for the ultimate purpose of providing mechanical force to tilt the gear boxes of the trowel assemblies. There are numerous varied configurations of steering linkage with most configured to provide some intuitive control for the operator, such as pushing the steering handles forward moves the power trowel in a forward direction, pulling back on the steering handles moves the trowel in a rearward direction, and tilting at least one steering handle tiltable to either the left or right to move the power trowel in the selected direction. A typical configuration for steering linkage is described in detail in the Best Mode section of this specification.
Whatever the configuration of the steering linkage, there must be at least one lever interconnecting the steering handles and the tiltable gear boxes for purposes of tilting them. This lever must pivot about one fixed point connected to the frame of the power trowel.
The problem is that riding power trowels are heavy, with most weighing between 500 lbs. to 1200 lbs. As a result, many attempts have been made to improve the mechanical advantage available to the operator through the steering handles, to assist the operator in tilting the gear boxes and the attached trowel assemblies from a flat at-rest position to a tilted position to control steering. One such example is found in the Allen, U.S. Pat. No. 5,108,220, wherein the tilting levers are attached at a pivot point at the rear of the machine, and extend substantially most of the way toward the front of the machine to provide a greater mechanical advantage to the operator. However, such extended leverage increases the weight of the machine, and the cost of fabrication of the riding power trowel. Also, the mechanical advantage gained from such devices is limited, and the operator is still required to apply considerable force to the steering handles in order to maintain control of the machine. Over several hours of operation, the operator can become fatigued and thus pose a threat to the safety of himself and others.
Accordingly, what is needed is a simple, lightweight assisted steering device which is capable of exerting considerable force to provide the mechanical advantage to the operator and thus to reduce the amount of force required to be expended by the operator to move the steering handles and thereby tilt the gear boxes of the trowel assemblies.